2000 Express 3500 Rumbling noise

[Thomas714]

I get this rumbling noise sometimes on startup
but not always it also happens frequently when
pulling off from a stop.It only seems to happen
going forward as I've never heard it in reverse.
It only lasts a few seconds and then runs normal.

I pulled the engine cover today to inspect things,
engine seems to twist a little but I don't think it's
excessive however I'm not sure. Mounts don't look
bad, but I could be wrong.

If anyone has a clue and can help I'd appreciate it
I suck at diagnosis and have read all the threads that seem related.

Thanks for your help in advance.

[Fecklar]

You may want to check your fan clutch. They have a tendency of getting seized. You should be able to easily move it with your hand while the engine is off.

[Thomas714]

Thanks for your reply, I checked that earlier the fan
turns okay. I found some heat shielding was loose
by the front wheel area on passenger side, it uses
some kind of washers with a star shaped middle to
fasten it down. A few were missing or not holding tight,
I guess they are a dealer item, was going to pick up some
tomorrow and see if that's it.

Thanks again for your response.